'\" t
.\"     Title: nvme-get-feature
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 10/20/2020
.\"    Manual: NVMe Manual
.\"    Source: NVMe
.\"  Language: English
.\"
.TH "NVME\-GET\-FEATURE" "1" "10/20/2020" "NVMe" "NVMe Manual"
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.SH "NAME"
nvme-get-feature \- Gets an NVMe feature, returns applicable results
.SH "SYNOPSIS"
.sp
.nf
\fInvme get\-feature\fR <device> [\-\-namespace\-id=<nsid> | \-n <nsid>]
                          [\-\-feature\-id=<fid> | \-f <fid>] [\-\-cdw11=<cdw11>]
                          [\-\-data\-len=<data\-len> | \-l <data\-len>]
                          [\-\-sel=<select> | \-s <select>]
                          [\-\-raw\-binary | \-b]
                          [\-\-human\-readable | \-H]
.fi
.SH "DESCRIPTION"
.sp
Submits an NVMe Get Feature admin command and returns the applicable results\&. This may be the feature\(cqs value, or may also include a feature structure if the feature requires it (ex: LBA Range Type)\&.
.sp
The <device> parameter is mandatory and may be either the NVMe character device (ex: /dev/nvme0), or a namespace block device (ex: /dev/nvme0n1)\&.
.sp
On success, the returned feature\(cqs structure (if applicable) may be returned in one of several ways depending on the option flags; the structure may parsed by the program and printed in a readable format if it is a known structure, displayed in hex, or the raw buffer may be printed to stdout for another program to parse\&.
.SH "OPTIONS"
.PP
\-n <nsid>, \-\-namespace\-id=<nsid>
.RS 4
Retrieve the feature for the given nsid\&. This is optional and most features do not use this value\&.
.RE
.PP
\-f <fid>, \-\-feature\-id=<fid>
.RS 4
The feature id to send with the command\&. Value provided should be in hex\&.
.RE
.PP
\-s <select>, \-\-sel=<select>
.RS 4
Select (SEL): This field specifies which value of the attributes to return in the provided data:
.TS
allbox tab(:);
lt lt
lt lt
lt lt
lt lt
lt lt
lt lt.
T{
Select
T}:T{
Description
T}
T{
0
T}:T{
Current
T}
T{
1
T}:T{
Default
T}
T{
2
T}:T{
Saved
T}
T{
3
T}:T{
Supported capabilities
T}
T{
4\(en7
T}:T{
Reserved
T}
.TE
.sp 1
.RE
.PP
\-l <data\-len>, \-\-data\-len=<data\-len>
.RS 4
The data length for the buffer returned for this feature\&. Most known features do not use this value\&. The exception is LBA Range Type
.RE
.PP
\-\-cdw11=<cdw11>
.RS 4
The value for command dword 11, if applicable\&.
.RE
.PP
\-b, \-\-raw\-binary
.RS 4
Print the raw feature buffer to stdout if the feature returns a structure\&.
.RE
.PP
\-H, \-\-human\-readable
.RS 4
This option will parse and format many of the bit fields into human\-readable formats\&.
.RE
.SH "EXAMPLES"
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Retrieves the feature for Number of Queues, or feature id 7:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme get\-feature /dev/nvme0 \-f 7
.fi
.if n \{\
.RE
.\}
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The following retrieves the feature for the LBA Range Type, which implicitly requires a buffer and will be printed to the screen in human readable format:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme get\-feature /dev/nvme0 \-f 3
.fi
.if n \{\
.RE
.\}
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Retrieves the feature for the some vendor specific feature and specifically requesting a buffer be allocate for this feature, which will be displayed to the user in as a hex dump:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme get\-feature /dev/nvme0 \-f 0xc0 \-l 512
.fi
.if n \{\
.RE
.\}
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
The following retrieves the feature for the LBA Range Type, which implicitly requires a buffer and will be saved to a file in its raw format:
.sp
.if n \{\
.RS 4
.\}
.nf
# nvme get\-feature /dev/nvme0 \-f 3 \-\-raw\-binary > lba_range\&.raw
.fi
.if n \{\
.RE
.\}
.sp
It is probably a bad idea to not redirect stdout when using this mode\&.
.RE
.SH "NVME"
.sp
Part of the nvme\-user suite
